In an interview recorded in France and aired on CNN's "State of the Union" on Sunday, Kerry said the government of Qatar, which agreed to keep watch on the men for a year, aren't the only ones with an eye on them.

When asked if that meant the United States would be monitoring them, Kerry wouldn't be specific, but said that if the former prisoners don’t meet the requirements of their release the United States has "the ability to do things."

"I'm not telling you that they don't have some ability at some point to go back and to get involved," Kerry said. "But they also have an ability to get killed doing that. And I don't think anybody should doubt the capacity of the United States of America to protect Americans."

He said that the freed Taliban detainee who already has vowed to return to kill more Americans is simply engaging in propaganda.

"Propaganda is propaganda, and they'll say whatever they want to stir the waters," he said.

As far as questions relating to Bergdahl's disappearance — some of his former platoon members say he walked away willingly — Kerry said there is plenty of time to sort through what happened now that Bergdahl is safe from enemy hands.

It would have been, he said, "offensive and incomprehensible to consciously leave an American behind … in the hands of people who would torture him, cut off his head."